JP2014041783A - Method for manufacturing solid state battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase charge/discharge capacity in a solid state battery having a Si negative electrode; and to provide porous carbon capable of providing a metal air battery improved in output characteristics while securing high capacity, and a metal air battery including the porous carbon in a positive electrode.SOLUTION: A method for manufacturing a solid state battery that includes a negative electrode containing Si as an active material, a positive electrode, and a Li-containing solid electrolyte disposed between the negative electrode and the positive electrode includes an initial charge/discharge treatment where an initial charging after the battery has been configured is performed while kept at a constant voltage for 20 hours or more so that a potential of a Si negative electrode becomes 20 mV(vs.Li/Li) or less, and then discharging is performed.

Description

  The present invention relates to a method for manufacturing a solid battery having a high charge specific capacity.

  With the miniaturization of personal computers, video cameras, mobile phones, etc., in the fields of information-related equipment and communication equipment, lithium secondary batteries have been put into practical use because of their high energy density as the power source used for these equipment. It has become widespread. On the other hand, in the field of automobiles, development of electric vehicles and hybrid vehicles is urgently caused by environmental problems and resource issues. Lithium secondary batteries are also being considered as power sources for electric vehicles and hybrid vehicles. Yes.

  Currently, carbon materials are generally used as negative electrode active materials for negative electrodes of lithium secondary batteries. Although the carbon material is inexpensive and easily available, there is a problem that a lithium secondary battery having a small amount of occlusion of Li and having a sufficient charge / discharge capacity cannot be obtained.

  In order to solve such a problem, research using a material other than a carbon material as a negative electrode active material has been conducted. For example, Patent Document 1 discloses a negative electrode for a secondary battery formed from a negative electrode containing Si.

JP 2000-340216 A

  The Si negative electrode is a high-capacity electrode, and high energy density can be expected in a battery using the above-described negative electrode containing Si. On the other hand, the secondary battery described in the cited document 1 uses an organic electrolyte solution that uses a flammable organic solvent as a solvent, and has a structure for preventing the installation of a safety device and preventing a short circuit that suppresses a temperature rise during a short circuit. Improvements in materials are necessary. In order to solve such a problem, a solid battery in which the liquid electrolyte is changed to a solid electrolyte has been proposed in recent years. However, when a Si negative electrode is used for the solid battery, there is a problem that the charge / discharge capacity is small.

In order to solve the above problems, according to the present invention, in a method for manufacturing a solid battery comprising a negative electrode containing Si as an active material, a positive electrode, and a solid electrolyte disposed between the negative electrode and the positive electrode, It is characterized in that it includes a first charge / discharge treatment in which the subsequent first charge is performed by holding the potential of the Si negative electrode at 20 mV (vs. Li ^/ Li ⁺ ) or less for 20 hours or more and then discharging.

  According to the method for producing a solid state battery of the present invention, the charge / discharge capacity is increased by performing the initial charging process.

It is a schematic sectional drawing of the solid battery of this invention. It is a graph which shows the measurement result of the charge specific capacity of the negative electrode of the battery in an Example and a comparative example.

  FIG. 1 shows the configuration of the solid state battery of the present invention. The solid battery 10 includes a negative electrode 1 containing Si as an active material, a positive electrode 2, and a solid electrolyte 3 containing Li disposed between the negative electrode and the positive electrode.

  The negative electrode 1 is formed from a material containing Si as an active material. As the material containing Si as an active material, crystalline or amorphous silicon alone or a compound containing silicon can be used. Examples of the silicon compound include inorganic silicon compounds such as silicon oxide, and organic silicon compounds such as silicone resins and silicon-containing polymer compounds that can be decomposed or reduced in a non-oxidizing atmosphere to change into silicon. Of these, silicon alone is particularly preferable. Further, the negative electrode 1 may be formed by compressing a negative electrode material powder containing Si, and the particle size of the powder is not particularly limited, but from the viewpoint of operability and the like, it may be 0.01 μm or more and 100 μm or less. preferable.

The material which comprises the positive electrode 2 will not be specifically limited if it has a function as a positive electrode active material, The thing used for a general solid lithium secondary battery can be used. For example, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiMn _2−x Ni _x O ₄ , LiMn _2−x Co _x O ₄ , LiMn _2−xy Ni _x Co _y O ₄ , LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ it can be used _{LiM 1-xy a x B y} O 2 or the like. Here, the general formula LiM _1-xy A _x B _y "M" O ₂ is at least one selected from the group consisting of Co, Ni, Mn or the like. “B” is “M” or “A”. Among the above, LiCoO ₂ and LiNiO ₂ are preferable, and LiCoO ₂ is particularly preferable. This is because LiCoO ₂ generally has good characteristics as a positive electrode active material and is widely used.

The solid electrolyte 3 is not particularly limited as long as it has a function as a solid electrolyte, and the same one as that used for a general solid lithium secondary battery can be used. For example, a sulfide-based solid electrolyte, thiosilicone, an oxide-based solid electrolyte, or the like can be used. Among the above, it is preferable to use a sulfide-based solid electrolyte and thiolithicone, and it is preferable to use a sulfide-based solid electrolyte material. This is because the sulfide-based solid electrolyte has high ionic conductivity, so that the output of the solid battery 10 can be increased. The negative electrode 1 and the positive electrode 2 may also contain the same solid electrolyte. Specifically, Li ₂ S—P ₂ S ₅ (Li ₂ S: P ₂ S ₅ = 50: 50 to 100: 0), Li ₂ S—P ₂ S ₅ —LiI, Li ₂ S—P ₂ S _{5 -Li 2 O-LiI, Li} 2 S-SiS 2, Li 2 S-SiS 2 -LiI, Li 2 S-SiS 2 -LiBr, Li 2 S-SiS 2 -LiCl, Li 2 S-SiS 2 -B _{2 S 3 -LiI, Li 2 S} -SiS 2 -P 2 S 5 -LiI, Li 2 S-B 2 S 3, Li 2 S-P 2 S 5 -Z m S n (Z = Ge, Zn, Ga _{), Li 2 S-GeS 2} , Li 2 S-SiS 2 -Li 3 PO 4, Li 2 S-SiS 2 -Li x MO y (M = P, Si, Ge, B, Al, Ga, In) or the like Can be mentioned. This solid electrolyte is preferably formed by compressing a solid electrolyte powder.

In the present invention, a battery is configured by disposing the negative electrode 1, the positive electrode 2, and the solid electrolyte 3 as shown in FIG. In the present invention, after this battery configuration, the potential of the Si negative electrode is 20 mV (vs. Li ^/ Li ⁺ ) or less, preferably 10 mV or less, so that the initial charge has a lower current density than usual. Manufactured by performing a constant voltage charge so as to hold for 10 hours or more, preferably 20 hours or more, and then performing a first charge / discharge treatment for discharging. By charging in advance at such a low current density, the Si negative electrode is activated, the interface between the negative electrode and the solid electrolyte is satisfactorily bonded, the Si alloy is amorphized, and the available capacity is large. It is considered to be.

Example 1
_{30LiI · 70 (0.08Li 2 O ·} 0.67Li 2 S · 0.25P 2 S 5) so that the mol% of the composition, Li ₂ S (Nippon Chemical Industrial), P ₂ S ₅ (Aldrich), LiI (Aldrich) And Li ₂ O (High Purity Chemical Laboratory) was put in a 45 ml ZrO ₂ container, 10 ZrO ₂ balls having a diameter of 10 mm were added, and the solid electrolyte was obtained by treatment at a platen rotation speed of 370 rpm for 40 hours. The positive electrode was made by attaching an In foil (Nilaco, φ10 mm, 0.1 mm thick Li foil (Honjo Chemical), and the negative electrode was made of Si powder (High Purity Chemical Laboratory) and the electrolyte powder produced above, Denka Black (Electrochemical Industry) was mixed in an agate mortar at a weight ratio of 75.6: 19.5: 4.9 to obtain a negative electrode powder.

80 mg of the above-mentioned electrolyte 30LiI · 70 (0.08Li ₂ O · 0.67Li ₂ S · 0.25P ₂ S ₅ ) was placed in a cylinder made of Macor (inner diameter φ10 mm) and pressed at 1 ton / cm ² . Next, 2 mg of the negative electrode powder was put in a cylinder and pressed at 4 ton / cm ² . Finally, the LiIn foil of the positive electrode was placed on the electrolyte opposite to the negative electrode, pressed at 1 ton / cm ² , and bolted at 6 Ncm to produce a battery cell.

The battery thus constructed was subjected to one cycle constant current-constant voltage discharge (initial charge / discharge treatment) in the range of −0.60 to 1 V (0.02 to 1.62 V vs. Li / Li ⁺ ) (current density 0.03 to 0.3 mA / cm). ² ). The constant current value is 0.3 mA, the constant voltage value 0.02V during discharge ^{(vs. Li / Li +)} , was ^{1.62V (vs. Li / Li +} ) during charging. Thereafter, charging and discharging were performed for 3 cycles at a current of 0.3 mA in the range of 0.02 to 1.62 V (vs. Li / Li ⁺ ).

Comparative Example 1
A battery cell was prepared in the same manner as in Example 1 and charged at a constant current of 3 cycles at 0.3 mA in the range of 0.02 to 1.62 V (vs. Li / Li ⁺ ) without performing the initial charge / discharge treatment in Example 1. Discharge was performed.

  The battery thus obtained was subjected to charge / discharge evaluation using a charge / discharge evaluation apparatus TOSCAT-3200 manufactured by Toyo System Co., Ltd. The charge specific capacity was calculated as the capacity per unit weight of Si contained in the Si negative electrode. The result is shown in FIG.

As described above, in Example 1, it was held at a constant voltage for 20 hours or more so that the Si negative electrode was 20 mV (vs. Li ^/ Li ⁺ ) only once in the initial stage so that the rate was lower than usual. While charging / discharging treatment was performed and then constant current charging / discharging was performed at 0.3 mA, in Comparative Example 1, constant current charging / discharging was performed at 0.3 mA without performing initial charging / discharging treatment. As a result, as shown in FIG. 1, a larger capacity was obtained in Example 1 than in Comparative Example 1. This is because once the charge / discharge is performed, the Si active material of the negative electrode is activated, the utilization rate is improved, and the interface between the Si active material and the solid electrolyte is well bonded, and the utilization rate is improved. Conceivable. Furthermore, although the crystalline Si negative electrode is alloyed with Li at about 0.1 V, it becomes amorphous once alloyed and the Li alloying potential starts from about 0.3 V, which is considered to be difficult to reach the cutoff potential. .

1 Negative electrode 2 Positive electrode 3 Solid electrolyte

Claims (4)

A method of manufacturing a solid battery comprising a negative electrode containing Si as an active material, a positive electrode, and a solid electrolyte containing Li disposed between the negative electrode and the positive electrode, wherein the first charge after the battery configuration is performed on the Si negative electrode A method for producing a solid state battery, comprising a first charge / discharge treatment in which a potential is 20 mV (Li / Li ⁺ ) or less for 20 hours or more and then discharged.   The method according to claim 1, wherein the initial charging is performed while maintaining a constant voltage.   The method according to claim 1, wherein the negative electrode is formed by compressing a negative electrode material powder containing Si.   The method according to claim 1, wherein the solid electrolyte is formed by compressing a solid electrolyte powder.

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